How To Calculate Power Ratings
by Website Staff
Many sports bettors use
basketball and football statistics to calculate power ratings
which gives them a convenient and useful ranking system. Power
ratings can also be used to create a mock pointspread. A difference between the pointspread created by
the sports bettor and the odds offered by the sportsbook may
indicate value for the bettor.
Basic Power Rating
Margin of victory, points scored minus points scored against is
the most common calculation used to formulate power ratiings. In
the following examples all teams have played four games.
a = game one margin of victory
b = game two margin of victory
c = game three margin of victory
d = game four margin of victory
e = number of games played
Basic PR = (a + b + c + d) /e + 100
Weighted Power Rating
It is logical to assume that a team's most recent results are
the best indicators of how they will perform in their next game.
To account for this tendency, it is necessary to give more
weight to recent games.
For each team multiply the margin of victory for every game by the numerical
order in whch it was played. The margin of victory for game one
is multiplied by 1, the margin of victory for game two is multiplied by 2 and so forth.
Therefore game four will have a weight of 4 which is twice as
much as game two and four times as much as game one. The
weighted margins for each team's games are added and
divided by the sum of the multipliers. After four games the
multiplier sum is ten. 1 + 2 + 3 + 4 = 10.
a = game one margin of victory
b = game two margin of victory
c = game three margin of victory
d = game four margin of victory
e = multiplier sum
Weighted PR = (a*1 + b*2 + c*3 + d*4) /e + 100
Final Power Rating
Unfortunately, basic power ratings do not consider a team's
strength of schedule. A more accurate power rating can be
calculated by averaging either a team's Basic PR or Weighted PR
with the power ratings from their
previous opponents.
u = team power rating
v = opponent one power rating
w = opponent two power rating
x = opponent three power rating
y = opponent four power rating
z = number of opponents
Final PR = (u + (v + w + x + y) /z) /2
Mock Pointspread
Power ratings can be used to predict the outcome of a game.
Subtract the Away Team PR from the Home Team PR, add 3.0 points
for home field advantage and multiply the result by (1). A negative pointspread
indicates a Home Favorite and a positive pointspread indicates a
Home Underdog.
Pointspread = ((Home Team PR  Away Team PR) + 3.0) *1
Example:
Home Team PR = 104.0
Away Team PR = 99.5
Pointspread
=
((104.0 – 99.5) + 3.0) *1 = 7.5
It is predicted that the home team will win the game by 7.5
points.
As the season progresses and data is collected the power
ratings will become more accurate, but It may be necessary to
rely on other handicapping techniques early in the schedule.
